The invention relates to aqueous solutions of sulfonated organosilicon compounds for use as starting materials, for example, for insoluble acid catalysts or for surface modification of inorganic materials. The novel method is characterized in that it is extremely economic and ecological, and it also can be used to produce aqueous solutions which contain no organic product apart from the sulfonated active component.
Sulfonated organosilicon compounds in insoluble form, as described in German Patent Application No. DE 32 26 093, are used more particularly as ion exchangers and solid acid catalysts (see also Acid-Base Catal., Proc. Int. Symp., 1988, pp. 379-396, edited by K. Tanabe, Tokyo, authors Y. Ono and S. Suzuki). These documents are entirely incorporated herein by reference.
In soluble form, preferably in aqueous solutions, these compounds are used as emulsifiers for reducing the surface tension of aqueous media or for surface modification of inorganic phases, for example, for producing chromatography phases.
The literature describes various methods of producing soluble sulfonated organosilicon compounds, silanes and siloxanes. For example, Great Britain Patent Application Nos. GB 1,270,977 and GB 1,198,096 describe the manufacture of sulfonated organosilicon compounds by reacting the corresponding epoxidized silane or siloxane with an amine sulfonate or with sodium bisulfite. These documents are entirely incorporated herein by reference. British Patent Application No. 1,005,872 (which is also entirely incorporated herein by reference) describes the manufacture of sulfonated organosilicon compounds obtained by reacting the corresponding unsaturated organosilicon compounds with an alkali metal bisulfite or an alkali metal pyrosulfite. In the case of British Patent Application No. 1,030,888, a mercaptoethyl silicon compound is reacted with sodium ethoxide and then with a hydroxypropane sulfonic acid. In German Patent Application No. DE-OS 38 08 174, organosilanes and organosiloxanes containing sulfone groups are obtained by oxidation of the corresponding mercaptopropyl-substituted starting compounds with sodium permanganate. These documents also are entirely incorporated herein by reference.
These known methods however have various disadvantages. The required reactants are either expensive or difficult to obtain. In the method of GB 1 005 872, the reaction has to be carried out under high pressure. In the case of DE-OS 38 08 174, manganese oxide occurs as a byproduct, and it is expensive to remove and dispose of.